This invention relates to the development of the high pressure glass column for high performance liquid chromatography.
Up to now, the stainless steel tube has been almost exclusively utilized for preparing a high pressure column in modern liquid chromatography. Although stainless steel is mechanically convenient material for designing and sealing up the end fitting of the high pressure column, it has some unfavorable features as follows: the packing material is not visible in the stainless steel tube, leading to difficulty in taking care of the packing materials and packing system during the operation; the column tube material itself is deteriorated by acid; and the inside wall of the tube is required to be polished up before use for reducing the unfavorable wall effect and for obtaining a high efficiency column.
As another alternative, a glass column tube has been proposed, because it is transparent permitting the sorbent packed in the column and the whole packing system to be visible, and the glass material itself is stable for acids and various chemicals.
However, the system for the design of the end fitting and sealing up of the column becomes difficult, because of the fragility of the glass material. Consequently, the end-fitting and sealing up-system of the column ends must be incorporated with some complex shock-absorbing mechanism such as an O-ring.
FIG. 1 shows an example of the column fitting system used for the glass column which has been conventionally available and indicates the cross section of one part of the column end. The end of the glass column tube 1 has a flange 2, and column fitting plug 4 which is inserted into the glass column tube 1 also has a flange 5. The narrow bore 3 for the effluent flow is provided in the center of the fitting plug 4. Between the two flanges 2 and 5, an O-ring is placed and the column fitting plug 4 and the column tube 1 are tightly screwed up by using the two male and female screws made of metal 7 and 8. A filter 9 is placed between the outlet of the column end fitting 4 and the packing material 10.
The complex structural mechanism of this system containing the male and female screws made of metal and the O-ring produces dead spaces in the inlet part of the column and unfavorable irregular eddy diffusion of the effluent takes place. Consequently, the eluent and the sample injected enter into the dead spaces and the column efficiency is decreased.
By the strong compression of the screws, the O-ring made of synthetic rubber or a fluorine-contained resin is often broken, leading to a leak of the effluent. As far as employing the O-ring in the column end fitting system, it is usually difficult to use the glass column for a high pressure of over 20 kg/cm.sup.2. This means that the slurry packing procedure by using high pressure, which is required for obtaining a high efficiency column is not able to be applied for such a glass column tube.
As a result, the glass column has been utilized only for the limited case of academic research and the analytical work involving the use of a strong acidic eluent as the mobile phase, which does not allow the use of a stainless steel column tube.
The purpose of this invention is to prepare a high efficiency glass column which can be used under a high pressure. In order to achieve this, the design of the system for the high pressure sealing of the column end fitting was widely examined.
By reducing the complexity of the conventional glass column system, the dead space involved in the column end fitting plug will be decreased, and therefore, the simplification of the design for the column end-fitting system excluding the use of an O-ring as well as with a high pressure sealing mechanism was desired.
A new high pressure sealing system allowing the application of the slurry packing procedure, and a simple sealing structure with no O-ring, affording the minimum dead space, was studied. As a result, a high pressure-high efficiecy column incorporating the minimized dead space in the column end fitting was realized.
The other items intended for this invention will be described in the following.